Current information indicates that the flavivirus virion contains three protein components, i.e. the glycosylated envelope protein (E), the non-glycosylated matrix protein (M) and the capsid protein (C). These proteins are proteolytic products of a long polyprotein precursor that is translated from a genomic-length RNA species. The genes coding for these viral structural proteins are clustered at the 5' terminus. We sought to provide evidence that the dengue virus genome also contains one open-reading frame and that the encoded polyprotein is processed to yield the individual viral proteins found in the virion and in infected cells. Using polyclonal antisera for immunoprecipitation, we have identified three dengue virion components of 51Kd, 14Kd, and 8Kd, respectively. These dengue-specific proteins are being prepared for determination of their amino-terminal amino acid sequence. In the meantime, cloned DNA segments located at the extreme 5'-end of the genome are being sequenced. These studies should enable us to determine the map positions of the genes that code for structural proteins. Also, the complete amino acid sequence of these structural proteins can be deduced from the cDNA sequence of their genes.